In Outlook Calenders there are duplicate/triplicate calender entries

Im guessing your duplicates are on your exhange data also.
You will need selected offline mode in 2011 office under the tools tab
Within outlook 2011 Under tools click sync services and disbale all if enabled.
Click Calendars in the navigation tab / right click the calendar in question / click folder properties / under the genral tab emtpy your cache / Notice your still offline so no exchange data will sync :)
You will need organise access to outlook web access and remove the calendar duplicates here first before you can re sync you outlook cleint on your local mac. If this exchange feature isnt enabled you need to conact your help desk / service desk and organise someone to remove the duplicates for you.
After this has been done you can switch online again and sync your calendars again and should kill the problem and shouldnt occur again.